An essay is a short literary composition on a particular theme or subject, usually in prose and generally analytic, speculative, or interpretative.
This is a sentence from Thomas Paine's famous essay "Common Sense."
The cause of America is in a great measure the cause of all mankind. Many circumstances hath, and will arise, which are not local, but universal, and through which the principles of all Lovers of Mankind are affected, and in the Event of which, their Affections are interested.